1. Field of the Invention
The present invention relates to a cable reel structure for mounting into a vehicle steering system e.g. for automobiles. The cable reel structure includes a fixed member and a mobile member (rotor part) mounted thereon in a freely rotatable manner. More particularly, the invention concerns a plurality of connector units mounted on the mobile member. In such connector units, connections can easily be established between electrical cables (external circuits) and bus bars (internal circuits).
2. Description of Background Information
A steering wheel of a vehicle generally contains an airbag and an inflator for inflating the airbag. In such a construction, the cable reel, i.e. rotary connector, serves as a means for connecting the inflator to the vehicle""s body side circuit. As shown in FIG. 1, the cable reel 1 includes a fixed member 2 that defines an external cylindrical portion and a bottom guard portion, and a mobile member 5 that defines an internal cylindrical portion and a top guard portion, the two members together forming a torus-shaped enclosure having a hollow inner space. As mentioned above, the mobile member 5 is mounted with the fixed member 2 in a freely rotatable manner. The fixed member 2 is then fixed with a combination switch body 3, which is in turn fixed to a steering column 4. Conversely, the mobile member 5 is fitted with a steering wheel. The torus-shaped enclosure contains a flat cable 6 in a spiraled condition. One end portion of the flat cable 6 is attached to the fixed member 2, while the other end portion is attached to the mobile member 5, so that the latter is connected to an external electrical cable. When the steering wheel is turned in a clockwise or counter-clockwise manner, the flat cable 6 is wound or unwound in conjunction with corresponding rotations of the mobile member 6.
The mobile member 5 includes a top guard portion carrying a connector unit 7, which projects towards the steering wheel. The flat cable 6 is connected to outside electrical circuits through the connector unit 7. When the number of outside circuits to be connected thereto is rather limited, the connector unit 7 may include only one array of pole cavities. However, when the number of outside circuits must be increased, the connector unit 7 may include two arrays of pole cavities, so as to form a multipolar configuration in the connector unit 7, as shown in FIG. 2.
Alternatively, the connector unit 7 may be divided into two subdivisions 7A and 7B located on different sites of the top guard portion, as shown in FIG. 3.
However, when the connector unit 7 is enlarged on a single site and the number of poles therein is increased, the number of electrical cables to be connected will be increased correspondingly. The end portions of the electrical cables will then become more entangled and difficult to handle. The structure of the connector unit 7 thus becomes more complex, and the number of steps for assembling the structure is increased.
Alternatively, as shown in FIG. 3, the connector unit 7 may be divided into two subdivisions 7A and 7B, which are placed at two symmetrically opposed positions on a diametrical center line of the mobile member 5.
In the above construction, the mobile member is mounted onto the fixed member which is immobilized at a fixed position. In such a construction, however, a plurality of connector units e.g. 7A and 7B cannot be welded successively simply by displacing the mobile member through a rotating action. For instance, a welding machine, equipped with an anvil 10 and a horn 11, must first be provided (shown in broken lines in FIG. 3). The anvil 10 and horn 11, once placed over the mobile member 5, are then reciprocated in a linear direction in the direction of the arrows in FIG. 3 while performing welding. Accordingly, when one of the subdivisions 7A and 7B is welded, the other, which is located diametrically opposite, must be placed in a position interfering with the anvil 10.
Accordingly, when the mobile member 5 is assembled with the fixed member 2, which is immobilized in turn, a plurality of subdivisions 7A and 7B can no longer be welded by an ultrasonic or resistance welder simply by effecting a rotating displacement of the mobile member 5.
Accordingly, the bus bars and electrical cables in the plurality of subdivisions 7A and 7B must be welded with the mobile member 5 not yet attached to the fixed member 2 and thus able to move up and down. Alternatively, the electrical cables may be connected to the connector units of the mobile member 5, before the latter is attached to the fixed member 2. However, in such a case, the assembling operation of the cable reel 1 will become very complicated.
In order to solve such problems, the present invention has been contemplated to provide a cable reel structure which includes a torus-shaped enclosure defined by a fixed member and a mobile member mounted thereon, the torus-shaped enclosure containing a flat cable or harness. The above mobile member includes a top guard portion, from which a plurality of connector units extend upwardly. The above flat cable or harness is then connected to bus bars. Subsequently, these bus bars are weld-bonded to the electrical cables in those connector units.
To this end, there is provided a cable reel structure configured to be mounted into a steering system for vehicles. The cable reel structure includes a fixed member, a mobile member having a top guard portion, and an enclosure having a diametrical center line and storing a flat cable. The flat cable contains several conductor elements respectively including a first end portion to be fixed to the fixed member and a second end portion to be fixed to the mobile member, such that the flat cable can be connected to outside circuits.
The second end portions of the conductor elements respectively include bus bars bonded thereto.
Further, the top guard portion of the mobile member includes at least first and second connector units adapted to receive the outside circuits, and each of the at least first and second connector units contains the bus bars extending there through.
The at least first and second connector units can then be placed in staggered positions with respect to the diametrical center line, such that, even after the mobile member has been mounted on the fixed member, welding of the bus bars to the outside circuits can be performed, successively in the at least first connector unit and the at least second connector unit, by rotating the mobile member after the welding has been performed in the at least first connector unit.
Preferably, the cable reel structure is defined by a fixed member and a mobile member so as to form a torus-shaped enclosure.
Preferably yet, the welding is performed by a welding machine including an anvil and a horn. The anvil and the horn form a working zone, within which they are moved closer to, or farther from, each other, while performing the welding in the at least first connector unit, and the staggered positions are defined such that the at least second connector unit is placed outside the working zone.
Suitably, the at least first and second connector units respectively include the same number of connector poles.
As mentioned above, a plurality of connector units are placed at staggered positions to one another. Accordingly, when the bus bars and outside circuits (electrical cables) in a first connector unit have been welded, the mobile member can be rotated around a fixed axis. The bus bars and outside circuits in a second connector unit are then welded without being impeded by the first connector unit. In this manner, welding operations can be performed even after the mobile member has been mounted onto the fixed member. Welding operations are thus carried out more efficiently, and are more amenable to automation.
Further, when the connector units are configured so as to each contain the same number of connector poles, welding can be effected using the same anvil welder body and horn welder body.
In another aspect of the present invention, a method is provided for assembling a cable reel structure for mounting in a steering system for automobiles. The method includes provision of a cable reel structure including a fixed member, a mobile member having a top guard portion and an enclosure having a diametrical center line and storing a flat cable. The flat cable contains several conductor elements respectively including a first end portion to be fixed to the fixed member and a second end portion to be fixed to the mobile member, such that the flat cable can be connected to outside circuits. The second end portions of the conductor elements respectively include bus bars bonded thereto.
The method may further include provision of at least first and second connector units on the top guard portion of the mobile member, which are adapted to receive the outside circuits. Each of the at least first and second connector units contains the bus bars extending therethrough. The at least first and second connector units are located at staggered positions with respect to the diametrical center line.
The method may further include welding of the bus bars to the outside circuits in the at least first connector unit, rotating the mobile member after the welding has been performed in the at least first connector unit and welding the bus bars to the outside circuits in the at least second connector unit.
In a further aspect of the present invention, the method utilizes a welding machine which includes an anvil and a horn which form a working zone within which they are moved closer to, or farther from, each other, during welding. The at least first connector unit is initially located within the working zone for welding of the bus bars to the outside circuits in the at least first connector unit. The at least second connector unit is initially located outside the working zone so as not to interfere with movement of the anvil and the horn during welding of the bus bars to the outside circuits in the at least first connector unit.
In a still further aspect of the present invention, rotation of the mobile member locates the at least second connector unit within the working zone for welding of the bus bars to the outside circuits in the at least second connector unit. Rotation of the mobile member also locates the at least first connector unit outside the working zone so as not to interfere with movement of the anvil and the horn during welding of the bus bars to the outside circuits in the at least second connector unit.
Further, the welding may include ultrasonic welding or resistance welding.